A Horse Was a Math Wiz: Clever Hans and Animal Intelligence

How one perceptive horse changed the understanding of animal intelligence forever.

The human dream to observe animal intelligence finally came true in 1891. In Berlin, a retired math teacher communicated with a horse through a series of nods and hoof taps. Together, they proved to crowds of people that animal intelligence was no hoax. Human/animal conversations were no longer limited to stories, such as the Indian fable with intuitive talking fish or the biblical story of Eve negotiating with a snake. No, Clever Hans, the Orlov Trotter stallion, spelled words and solved math equations with his owner and teacher, Wilhelm von Osten.

When the Cat and Bear Failed, He Tried the Horse

Clever Hans and Wilhelm von Osten / Landes Bioscience

Wilhelm von Osten devoutly believed in greater animal intelligence. Even after his failed experimentation with cats and bears, he maintained his beliefs. As a phrenologist, he claimed the shape and size of a brain made all the difference in determining an animal’s mental abilities (a theory that has since been disproven). That’s why he sought out Hans the horse.

The Orlov Trotter is a horse bred to love people and learn quickly. Due to these traits and years of training, Hans did exceptionally well with von Osten’s instruction — so well that a Hans Commission was formed to debunk what was viewed as an impossible display of animal intelligence.

But the diverse team on the Hans Commission did no such disproving (they said he was legit) until a still-speculative psychologist named Oskar Pfungst formulated a plan to crack the code. He spent years doing experiments that sometimes involved isolating Hans in a tent where he couldn’t have the positive reinforcement of endearing crowds. Although Hans had already passed tests conducted by people other than von Osten, Pfungst decided to isolate the human factor altogether. These variables made for a discovery even more profound than the original claim — one that changed the studies of animal behaviorists forever.

Deception vs. Perception

Clever Hans and crowd / Creative Commons

It turned out that Hans was so perceptive about minuscule human movements, gestures, heart rates and other slight behavior cues that he could determine a correct answer to a question. If the person administering the test didn’t know the answer, Hans didn’t answer correctly. If a human delivering the question was eliminated altogether, Hans’ success rate dropped from nearly 100% to 0%.

Because von Osten wore a wide-brimmed hat, his gestures were unintentionally more pronounced. Clever Hans was so tuned in to his subtle motions that even the slightest relief or tension would prompt a corresponding action.

This validated the viewpoint of many skeptics who’d doubted animal intelligence all along. Even the animal behaviorists of today must carefully defend their research on animal intelligence. Because of Clever Hans, they must always use a double-blind experiment to keep any human influence at bay.

My Dog Has ESP

Getty Images

Animals with ESP can easily get filed under the “internet wormhole” category. For years, pet psychics and animals with supernatural abilities have occupied pages upon pages of YouTube search results. Cats are suddenly telling people they’re so angry because this food they’re being served is simply a disgrace to their species!

All kidding aside, it’s true that most people consider pets their surrogate children. They feel a connection so deep that communication with them is like an additional, secret language.

Sonya Fitzpatrick, a favorite pet psychic among pet-loving celebrities, has built a career around this specialized communication. Jocelyn Kessler wrote a book about her pet talk, using it as a how-to tool for better pet ownership. We can’t forget about Hollywood Dog Whisperer Cesar Milan and self-proclaimed Cat Daddy Jackson Galaxy. Whole television shows detail their experiences exploring the mysterious nature of our furry friends.

Angela Weiss / Getty Images

Human fascination with animal intelligence clearly hasn’t faded since 1891. These celebrities and “psychics” have popularized what animal behaviorists commonly stand behind: that thanks to Clever Hans and the discovery made by Oskar Pfungst, we now know animals are extremely specialized. Rather than mastering a human set of behaviors, they are simply observing and using their own version of intelligence to respond to subtle human clues. In a sense, they’ve become masters of human behavior, rather than the other way around. Extrasensory perception, indeed.

With the help of pet psychics and whisperers, a larger audience has a greater appreciation for animal intelligence. What psychics may call “tuning in to the energy of the heart center,” we may better understand this way: language is not the only form of sharing communication.

Training Pets for the Big Screen and Other Work

On the set of Lassie (2005) / Paramount Pictures

Similar to a pet psychic, becoming an animal trainer in Hollywood requires a focused understanding of animal behavior. It also requires a long-term bond between trainer and trainee. Imagine an FDA-employed dog sniffing out the bad guys without strong ties to their human supervisor. It just wouldn’t work.

Clever Hans responded to positive reinforcement from adoring crowds. Today animal trainers use operant conditioning to show an animal they’re correctly performing the desired action. This is why a trainer at the zoo throws fish to a sea lion between tricks.

Animal trainer Teresa Ann Miller explains that subtleties must be drawn out to encourage an animal to behave a certain way for the camera. Instead of using quick reactions to short and sharp commands, trainers for the big screen use elongated, drawn-out expressions for a certain result. This keeps an animal guessing, slowly trying to decipher the information the human is giving them.

Training animals for television and movies has evolved to a sophisticated understanding of how animals relate to humans’ physical cues. Enter Lassie, Mr. Ed and Babe, all animals who required the assistance of stunt doubles, computer animation and good trainers.

Closing with a Lesson

Clever Hans is now a cautionary symbol who’s posed much speculation and frustration among a variety of scholars. In fact, a 1980 linguistic conference titled “The Clever Hans Phenomenon” actually tried to ban any further study of animal language.

Their attempts failed. The octopus Pulpo Paul was still revered for miraculously determining the 2010 World Cup results. Alex the Parrot proved he had vocal, cognitive abilities beyond mimicking. Penny Patterson continued to teach Koko the Gorilla sign language at Stanford. And books have been published on why elephants weep.

As Doctor Dolittle’s parrot Polynesia says, “Animals don’t always speak with their mouths.” She raises her eyebrows and continues in a high voice, “They talk with their ears, with their feet, with their tails — with everything. Sometimes they don’t want to make a noise… People, golly! I suppose if people ever learn to fly — like any common hedge-sparrow — we shall never hear the end of it!”